Taxation wasn't necessarily extracted in silver or coinage in early medieval Scandinavian society; rather, according to sagas like Egils saga, it was taken in resources; things like fur, food, salt, amber, timber, etc. were presented as tribute or taxation to local kings (keeping in mind that the viking era arguably ended when centralized kingship became a thing, thus concentrating on local kings and petty-kingdoms.)

As far as military service goes, all land-owners were considered retainers of their jarls or konungar and would provide military service to them if needed. Individual landowners in mainland Scandinavia would rarely (if ever) go víking without their jarl or konungr giving them permission to do so and assisting with outfitting and crewing their ships, which required a lot of resources the average landowner didn't have. In Iceland the individual setting up the expedition would hire other farmers and landowners to accompany them.

Once a víking was completed and the ship(s) returned home, the spoils would be divvied up in an agreed upon manner and, if the jarl or konungr hadn't received his payment beforehand, he would be paid for outfitting the ship and crew (assuming he hadn't accompanied them in the first place - usually, it was at their initiative that a víking was launched)

Hope that answers your questions.